Fix non-JSON logging in sockets.py and state.py

- Fix literal string '{event}' in error logs (sockets.py lines 145, 163)
  The string was not an f-string, so {event} was logged literally instead
  of the actual event data. Changed to use proper logging format args.

- Fix model_dump() returning non-JSON-serializable objects (state.py)
  The model_dump() method returns Python objects like UUID and enums
  that appear as repr strings in logs (e.g., UUID('...'), <Enum.VALUE>).
  Changed to use model_dump(mode='json') wrapped in json.dumps() for
  proper JSON-serializable output.

Co-authored-by: openhands <openhands@all-hands.dev>

Author: openhands-agent

openhands-agent-server/openhands/agent_server/sockets.py

@@ -142,7 +142,9 @@ async def _send_event(event: Event, websocket: WebSocket):
         dumped = event.model_dump(mode="json")
         await websocket.send_json(dumped)
     except Exception:
-        logger.exception("error_sending_event:{event}", stack_info=True)
+        logger.exception(
+            "error_sending_event: %s", getattr(event, "id", str(event)), stack_info=True
+        )
 
 
 @dataclass
@@ -160,7 +162,11 @@ async def _send_bash_event(event: BashEventBase, websocket: WebSocket):
         dumped = event.model_dump(mode="json")
         await websocket.send_json(dumped)
     except Exception:
-        logger.exception("error_sending_event:{event}", stack_info=True)
+        logger.exception(
+            "error_sending_bash_event: %s",
+            getattr(event, "id", str(event)),
+            stack_info=True,
+        )
 
 
 @dataclass

openhands-sdk/openhands/sdk/conversation/state.py

@@ -251,8 +251,8 @@ def create(
 
             logger.info(
                 f"Resumed conversation {state.id} from persistent storage.\n"
-                f"State: {state.model_dump(exclude={'agent'})}\n"
-                f"Agent: {state.agent.model_dump_succint()}"
+                f"State: {json.dumps(state.model_dump(exclude={'agent'}, mode='json'))}\n"
+                f"Agent: {json.dumps(state.agent.model_dump_succint())}"
             )
             return state
 
@@ -278,8 +278,8 @@ def create(
         state._autosave_enabled = True
         logger.info(
             f"Created new conversation {state.id}\n"
-            f"State: {state.model_dump(exclude={'agent'})}\n"
-            f"Agent: {state.agent.model_dump_succint()}"
+            f"State: {json.dumps(state.model_dump(exclude={'agent'}, mode='json'))}\n"
+            f"Agent: {json.dumps(state.agent.model_dump_succint())}"
         )
         return state